It has been shown that electromagnetic energy transfer between a hot and a cold body is a function of the close spacing of the bodies due to evanescent coupling of near fields. Thus, the closer the bodies, approximately one micron and below, the greater the power transfer. For gap spacings of 0.1 microns, increases in power output of factors often are common.
The dilemma, however, is maintaining the close spacing at a sub-micron gap in order to maintain the enhanced performance.
While it is possible to obtain the sub-micron gap spacing, the thermal effects on the hot and cold surfaces induce cupping, warping or deformation of the elements resulting in variations in gap spacing thereby resulting in uncontrollable variances in the power output.
Typically, in order to increase power output, given the lower power density of prior devices, it has been necessary to increase the temperature. However, the temperature increase is limited by the material of the device.